Photosynthetic Biohybrid Coculture For Tandem And Tunable CO₂ And N₂ Fixation

Authors

Stefano Blanco, University of California, Berkeley
Rachel R. Chan, University of California, Berkley
Yue Xiao Shen, University of California, Berkeley
Ji Min Kim, University of California, Berkeley
Tom A. Tacken, University of California, Berkley
Rhesa Ledbetter, University of California, Berkeley
Sunmoon Yu, University of California, Berkeley
Lance C. Seefeldt, University of California, Berkeley
Peidong Yang, University of California, Berkeley

Document Type

Article

Journal/Book Title

Proceedings of the National Academy of Sciences of the United States of America

Publication Date

6-21-2022

Publisher

National Academy of Sciences

Volume

119

Issue

26

First Page

1

Last Page

10

Abstract

Solar-driven bioelectrosynthesis represents a promising approach for converting abundant resources into value-added chemicals with renewable energy. Microorganisms powered by electrochemical reducing equivalents assimilate CO2, H2O, and N2 building blocks. However, products from autotrophic whole-cell biocatalysts are limited. Furthermore, biocatalysts tasked with N2 reduction are constrained by simultaneous energy-intensive autotrophy. To overcome these challenges, we designed a biohybrid coculture for tandem and tunable CO2 and N2 fixation to value-added products, allowing the different species to distribute bioconversion steps and reduce the individual metabolic burden. This consortium involves acetogen Sporomusa ovata, which reduces CO2 to acetate, and diazotrophic Rhodopseudomonas palustris, which uses the acetate both to fuel N2 fixation and for the generation of a biopolyester. We demonstrate that the coculture platform provides a robust ecosystem for continuous CO2 and N2 fixation, and its outputs are directed by substrate gas composition. Moreover, we show the ability to support the coculture on a high-surface area silicon nanowire cathodic platform. The biohybrid coculture achieved peak faradaic efficiencies of 100, 19.1, and 6.3% for acetate, nitrogen in biomass, and ammonia, respectively, while maintaining product tunability. Finally, we established full solar to chemical conversion driven by a photovoltaic device, resulting in solar to chemical efficiencies of 1.78, 0.51, and 0.08% for acetate, nitrogenous biomass, and ammonia, correspondingly. Ultimately, our work demonstrates the ability to employ and electrochemically manipulate bacterial communities on demand to expand the suite of CO2 and N2 bioelectrosynthesis products.

Comments

Copyright © 2022 National Academy of Sciences. All rights reserved.

Recommended Citation

Cestellos-Blanco, S., Chan, R. R., Shen, Y., Kim, J. M., Tacken, T. A., Ledbetter, R., Yu, S., Seefeldt, L. C., and Yang, P. (2022) Photosynthetic biohybrid coculture for tandem and tunable CO2 and N2 fixation. Proc. Natl. Acad. Sci. U. S. A.119, e2122364119.